The present invention relates to optical scanning devices and more specifically to a raster variation method for omnidirectional optical scanners.
Optical scanners are well known for their usefulness in retail checkout and inventory control. Optical scanners generally employ a laser diode, the light from which is focused and collimated to produce a scanning beam. An optical transceiver directs the beam against a plurality of stationary pattern mirrors to form multiple lines and collects the scanning light after it is reflected by a bar code label. A motor rotates the optical transceiver, and a detector receives the returning beam. An example of an optical scanner can be found in commonly assigned U.S. Pat. No. 4,971,410, entitled, "Scanning and Collection System for a Compact Laser", issued Nov. 20, 1990, to Wike, Jr. et al. This patent is hereby incorporated by reference.
The more lines a scan pattern has, the more efficient scanning operations are. Unfortunately, the number of scan lines produced by prior art scanners is determined by the number of scanning beams generated, which is determined by the number of stationary pattern mirrors used. Depending on the size of the bar code label to be read, prior optical scanners have employed interchangeable scanning heads, which produce different scan patterns which vary in the size and the number of scan lines forming the scan pattern.
Therefore, it would be desirable to generate a scan pattern having a density of scan lines sufficient to allow an optical scanner to scan different size bar code labels with the same reading efficiency. It would also be desirable to vary this scan pattern to match the aspect ratio of the bar code label.